1. Field of the Invention
The invention relates to the manufacture of sintered metal articles particularly, but not exclusively, sealing rings in the range from 12 mm to 25 mm diameter, for use either as shaft seals or as sealing rings in reciprocating piston and cylinder devices such as shock absorbers.
Articles produced by sintering metal powders generally contain internal pores. These pores are disadvantageous in that they reduce the strength and modulus of elasticity of the article in comparison with similar articles produced, for example, by casting and forging.
2. Description of the Prior Art
Two known proposals for overcoming these disadvantages have been to spray copper onto the surface of the article or to place copper powder or a piece of copper or copper alloy of appropriate shape on the surface of the article and then heat the copper or copper alloy and the article to a temperature above the melting point of the copper or copper alloy so that the copper or copper alloy infiltrates the pores. It is desirable that the weight of copper applied to the article be carefully controlled so that there is sufficient copper to fill the pores but not an excess of copper.
It is a disadvantage of such previous proposals that, in the case of articles of small size and weight where very small quantities of copper or copper alloy are required, the quantity of copper or copper alloy associated with the sintered article cannot be closely controlled, due to the way in which the copper or copper alloy is applied.